PV Diagram help - Monatomic ideal gas change of state

AI Thread Summary
The discussion focuses on calculating the work done on a monatomic ideal gas during a change of state from A to D on a PV diagram, with the work calculated as 1215.6 J for the constant volume and constant pressure paths. The main challenge arises in determining the change in internal energy without knowing the number of moles or temperature. It is clarified that internal energy depends on temperature, and the user suggests using the ideal gas law to express internal energy in terms of pressure and volume. Ultimately, the user resolves the issue and expresses gratitude for the assistance received.
prj
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Homework Statement


Suppose a monatomic ideal gas is changed from state A to state D by one of the processes shown on the PV diagram (attached). a) Find the total work done on the gas if it follows the constant volume path A-B followed by the constant pressure path B-C-D. b)Calculate the total change in internal energy of the gas during the entire process and the total heat flow into the gas.

Homework Equations



W= -P(Vf-Vi)
dU = Q + W
dU = 3/2nRT

The Attempt at a Solution


I found the answer to part A to be 1215.6 J of work were done on the gas. My problem comes in part b. How can I determine the change in internal energy without knowing the number of moles (n) of the gas, or the temperature?
 

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Do you really need n to calculate the change in internal energy? Remember that U depends only on temperature, so what is the temperaure difference?
 
prj said:
dU = 3/2nRT

How can I determine the change in internal energy without knowing the number of moles (n) of the gas, or the temperature?

Shouldn't that be dU = 3/2nRdT? Or ΔU = Δ(3/2nRT)? Maybe you can use the ideal gas law to write this in terms of P and V rather than nRT.
 
I think I was over-complicating the problem, but I've solved it now.

Thank you for the help!
 
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